GB1582846A

GB1582846A - Steering wheels

Info

Publication number: GB1582846A
Application number: GB4934276A
Authority: GB
Original assignee: TRW Clifford Ltd
Current assignee: TRW Clifford Ltd
Priority date: 1978-01-30
Filing date: 1978-01-30
Publication date: 1981-01-14

Description

.(54) STEERING WHEELS (71) We, TRW CLIFFORD LIMITED, a British company of DuPont House, 101 Vaughan Way, Leicester LE1 4SA, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to steering wheels for motor vehicles.

According to the present invention, there is provided a steering wheel having a central portion, a rim, and at least one arm connecting the central portion with the rim; said rim, said at least one arm and said central portion comprising a reinforcing core and a moulded plastics outer covering extending over at least part of the core, said reinforcing core being formed of compression moulded layers of fibre-reinforced plastics sheet in which the fibres are orientated and wherein the direction(s) of orientation of the fibres in at leàst one of the sheets is/are different from the direction(s) of orientation of the fibres in at least one of the other sheets.

Preferably, the portion of the outer covering on the or each arm of the steering wheel is of relatively thin, substantially constant section.

The Applicants have found that, if the reinforcing core is formed so that it is of the same shape as but slightly smaller than the final steering wheel at least in the region of the or each arm, the problem of sinkage in those regions which are prone to sinkage can be obviated or mitigated due to the avoidance of a relatively thick variable section in such regions.

The ideal thickness of the outer covering depends basically upon the co-efficient of thermal expansion of the particular synthetic plastics material chosen for the outer covering as well as the physical properties required of the outer covering. Generally speaking, an outer covering thicknes of about 3 mm is considered suitable.

The sheets may be interleaved with one or more layers of reinforcing fibres, -e.g.

woven or non-woven fibre matt.

The or each sheet may be pre-cut so that' it comprises an outer annular rim portion, a central portion spaced inwardly of the rim portion and at least dne arm portion extend- ing between the central and rim portions; and being integral therewith.

The reinforcing core may be provided with a 'moulded in, or bolted on; splined metal member to enable the steering wheel to be attached to the steering column of the motor vehicle.

The reinforcing core may be formed of a fibre-reinforced thermoplastics or thermo- setting resin sheet. For example, it may be formed of glass and/or carbon fibre rein forced nylon, polyethylene, polypropylene or polyester sheet.

The outer covering may be formed of polypropylene, P;V.C., cellulose acetate, cellulose acetate butyráte, or a thermo plastic polyurethane. Generally, the outer covering will be formed of an unfoamed plastics material although it is within the scope of the present invention to provide an outer covering formed of a foamed plastics material. The provision of the relatively thin outer covering-also enables a higher quality, and therefore higher cost, material to be employed without appreciably increasing the cost of the steering wheel.

The outer covering of the steering wheel may have any suitable finish, for example a leather grain finish. The surface of the reinforcing core may be roughened or suit ably recessed to provide a key for the outer covering so thát the risk of stripping of the outer covering from the core is minimized.

An embodiment of the present invention will now be described, by way of example, with reference-to the accompanying drawing, 'in which: Fig. 1 is a plan view of one embodiment of the steering wheel according to the pre sent invention, Fig. 2 is a section of part of the steering wheel of Fig. 1.

Referring to the drawing, the steering wheel generally compries a central portion or, boss 10, a rim 11, and four arms 12 extending between the rim 11 and the boss 10 and serving to mount the rim 11 on the boss -10.

The boss 10, rim 11 and arms 12 are formed of a reinforcing core 13 and an outer covering 14 (see Fig. 2). The reinforcing core 13 is similar in shape but slightly smaller than the finished steering wheel.

The reinforcing core 13 is formed of a plurality of pre-cut sheets of a thermoset polyester resin sheet moulding composition containing 25% by weight of specifically orientated glass fibres. Each pre-cut sheet comprises an annular rim portion 15 of circular cross-section, four arm portions 16 and a central portion 17, these various portions 15, 16 and 17 being shown collectively in Fig. 2. The portions 15, 16 and 17 of each pre-cut sheet are integral with one another.

The compression moulding operation of the core 13 is effected by stacking the precut sheets into a die into which has been previously disposed a die-cast, integrally splined insert 18 in the region of the boss 10, and then applying heat and pressure to mould and cure the resin. The cutting and stacking of the sheets is such that the fibre orientations in at least two sheets are relatively staggered.

The outer covering 14 is formed by inserting the moulded reinforcing core 13 complete with insert 18 into a further die and then injection moulding unfoamed polypropylene into the die around the core 13 so that the latter is completely covered, except for a bore 19 in the boss portion 17, with the polypropylene outer covering 14 to a substantially constant thickness of 3 mm over the portions 15 and 16. The splined insert 18 is, however, not coated on its splined surface with the polypropylene covering 14. The internal surface of the injection moulding die is textured to impart a leather grain effect to the external surface of the covering 14.

Because of the thin, substantially constant section of the covering 14, there is no visible sinkage on the surface of the steering wheel.

It will be manifest that shape of the core 13 is dictated not only by the physical characteristics of the steering wheel, such as impact resistance and flexural strength com bined with minimum weight, but also by the intended shape of the steering wheel sq.as to enable the previously-men'floned problems of sinkage in the region of tlie arms 1-2.

WHAT WE CLAIM IS : - 1. A steering wheel - having a central portion, a rim, and at least one arm connect-ing the central portion with the rim; -s-aid rim, said at least one arm and said central portion comprising a reinforcing core and a moulded plastics outer covering' e'xt'ending over at least part of the core, said rein forcing core being formed of compression moulded layers of fibre-reinforced plastics sheet in which the fibres are orientated and wherein the direction(s) of orientation of the fibres in at least one of the sheets is/are different from the direction(s) of orientation of the fibres in at least one of the other sheets.

2. A steering wheel as claimed in claim 1, wherein the portion of the outer covering on the or each arm of the steering wheel is of relatively thin, substantially constant section.

3. A steering wheel as claimed in claim 1 or 2, wherein the sheets are interleaved with one or more layers of reinforcing fibres.

4. A steering wheel as claimed in claim 1, 2 or 3, wherein each sheet is pre-cut so that it comprises an outer annular rim portion, a central portion spaced inwardly of the rim portion and at least one arm portion extending between the central and rim portions, and being integral therewith.

5. A steering wheel as claimed in any preceding claim, wherein the reinforcing core is provided with a moulded-in splined metal member to enable the steering wheel to be attached to a steering column of a motor vehicle.

6. A steering wheel as claimed in any one of claims 1 to 4, wherein the reinforcing core is provided with a bolted-on splined metal member to enable the steering wheel to be attached to a steering column of a motor vehicle.

7. A steering wheel substantially as here inbefore described with reference to the accompanying drawings.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. Referring to the drawing, the steering wheel generally compries a central portion or, boss 10, a rim 11, and four arms 12 extending between the rim 11 and the boss 10 and serving to mount the rim 11 on the boss -10. The boss 10, rim 11 and arms 12 are formed of a reinforcing core 13 and an outer covering 14 (see Fig. 2). The reinforcing core 13 is similar in shape but slightly smaller than the finished steering wheel. The reinforcing core 13 is formed of a plurality of pre-cut sheets of a thermoset polyester resin sheet moulding composition containing 25% by weight of specifically orientated glass fibres. Each pre-cut sheet comprises an annular rim portion 15 of circular cross-section, four arm portions 16 and a central portion 17, these various portions 15, 16 and 17 being shown collectively in Fig. 2. The portions 15, 16 and 17 of each pre-cut sheet are integral with one another. The compression moulding operation of the core 13 is effected by stacking the precut sheets into a die into which has been previously disposed a die-cast, integrally splined insert 18 in the region of the boss 10, and then applying heat and pressure to mould and cure the resin. The cutting and stacking of the sheets is such that the fibre orientations in at least two sheets are relatively staggered. The outer covering 14 is formed by inserting the moulded reinforcing core 13 complete with insert 18 into a further die and then injection moulding unfoamed polypropylene into the die around the core 13 so that the latter is completely covered, except for a bore 19 in the boss portion 17, with the polypropylene outer covering 14 to a substantially constant thickness of 3 mm over the portions 15 and 16. The splined insert 18 is, however, not coated on its splined surface with the polypropylene covering 14. The internal surface of the injection moulding die is textured to impart a leather grain effect to the external surface of the covering 14. Because of the thin, substantially constant section of the covering 14, there is no visible sinkage on the surface of the steering wheel. It will be manifest that shape of the core 13 is dictated not only by the physical characteristics of the steering wheel, such as impact resistance and flexural strength com bined with minimum weight, but also by the intended shape of the steering wheel sq.as to enable the previously-men'floned problems of sinkage in the region of tlie arms 1-2. WHAT WE CLAIM IS : -

1. A steering wheel - having a central portion, a rim, and at least one arm connect-ing the central portion with the rim; -s-aid rim, said at least one arm and said central portion comprising a reinforcing core and a moulded plastics outer covering' e'xt'ending over at least part of the core, said rein forcing core being formed of compression moulded layers of fibre-reinforced plastics sheet in which the fibres are orientated and wherein the direction(s) of orientation of the fibres in at least one of the sheets is/are different from the direction(s) of orientation of the fibres in at least one of the other sheets.